1. Field of the Invention
This invention relates to cryosurgical probes and more particularly to a cryosurgical probe that includes an improved malleable shaft for use with applications in which a desired angle of entry and contact with the patient""s organ is required.
2. Description of the Related Art
Cryosurgical probes are used to treat a variety of diseases. The cryosurgical probes quickly freeze diseased body tissue, causing the tissue to die after which it will be absorbed by the body, expelled by the body, sloughed off or replaced by scar tissue. Cryothermal treatment is currently used to treat prostate cancer and benign prostate disease, breast tumors including breast cancer, liver tumors including cancer, glaucoma and other eye diseases. Cryosurgery may also be used for the treatment of a number of other diseases and conditions including the treatment of cardiac arrhythmias, such as atrial fibrillation.
A variety of cryosurgical instruments variously referred to as cryoprobes, cryosurgical probes, cryosurgical ablation devices, and cryostats and cryocoolers, have been available for cryosurgery. These devices typically use the principle of Joule-Thomson expansion to generate cooling. They take advantage of the fact that most fluids, when rapidly expanded, become extremely cold. In these devices, a high pressure gas such as argon or nitrogen is expanded through a nozzle inside a small cylindrical shaft or sheath typically made of steel, and the Joule-Thomson expansion cools the steel sheath to a cold temperature very rapidly.
An exemplary device is illustrated in Sollami, Cryogenic Surgical Instrument, U.S. Pat. No. 3,800,552 (Apr. 2, 1974). Sollami shows a basic Joule-Thomson probe with a sheath made of metal, a fin-tube helical gas supply line leading into a Joule Thomson nozzle which directs expanding gas into the probe. Expanded gas is exhausted over the fin-tube helical gas supply line, and pre-cools incoming high pressure gas. For this reason, the coiled supply line is referred to as a heat exchanger, and is beneficial because, by pre-cooling incoming gas, it allows the probe to obtain lower temperatures.
Ben-Zion, Fast Changing Heating and Cooling Device and Method, U.S. Pat. No. 5,522,870 (Jun. 4, 1996) applies the general concepts of Joule-Thomson devices to a device that is used first to freeze tissue and then to thaw the tissue with a heating cycle. Nitrogen is supplied to a Joule-Thomson nozzle for the cooling cycle, and helium is supplied to the same Joule-Thomson nozzle for the warming cycle. Preheating of the helium is presented as an essential part of the invention, necessary to provide warming to a sufficiently high temperature.
A Joule-Thomson cryostat for use as a gas tester is illustrated in Glinka, System for a Cooler and Gas Purity Tester, U.S. Pat. No. 5,388,415 (Feb. 14, 1995). Glinka also discloses use of the by-pass from the Joule-Thomson Nozzle to allow for cleaning the supply line, and also mentions that the high flow of gas in the by-pass mode will warm the probe. This is referred to as mass flow warming, because the warming effect is accomplished purely by conduction and convection of heat to the fluid mass flowing through the probe.
Various cryocoolers use mass flow warming, flushed backwards through the probe, to warm the probe after a cooling cycle. Lamb, Refrigerated Surgical Probe, U.S. Pat. No. 3,913,581 (Aug. 27, 1968) is one such probe, and includes a supply line for high pressure gas to a Joule-Thomson expansion nozzle and a second supply line for the same gas to be supplied without passing through a Joule-Thomson nozzle, thus warming the catheter with mass flow. Longsworth, Cryoprobe, U.S. Pat. No. 5,452,582 (Sep. 26, 1995) discloses a cryoprobe which uses the typical fin-tube helical coil heat exchanger in the high pressure gas supply line to the Joule-Thomson nozzle. The Longsworth cryoprobe has a second inlet in the probe for a warming fluid, and accomplishes warming with mass flow of gas supplied at about 100 psi. The heat exchanger, capillary tube and second inlet tube appear to be identical to the cryostats previously sold by Carleton Technologies, Inc. of Orchard Park, N.Y.
Each of the above mentioned cryosurgical probes builds upon prior art which clearly establishes the use of Joule-Thomson cryocoolers, heat exchangers, thermocouples, and other elements of cryocoolers. Walker, Miniature Refrigerators for Cryogenic Sensor and Cold Electronics (1989) (Chapter 2) and Walker and Gingham, Low Capacity Cryogenic Refrigeration, pp. 67 et seq. (1994) show the basic construction of Joule-Thomson cryocoolers including all of these elements. The Giaque-Hampson heat exchanger, characterized by coiled finned-tube, transverse flow recuperative heat exchanger is typical of cryocoolers. The open mandrel around which the finned tube coil is placed is also typical of cryocoolers.
U.S. Pat. Nos. 5,800,487 and 6,074,412, both entitled Cryoprobe, issued to Mikus et and assigned to the present assignee disclose cryoprobes using Joule-Thomson nozzles and finned tube helical coil heat exchangers.
Cryosurgical probes may be used, as mentioned above, to treat diseases of the prostate, liver, and breast, and they have gynecological applications as well. The cryosurgical probes form iceballs which freeze disease tissue. Each application has a preferred shape of iceball, which, if capable of production, would allow cryoablation of the diseases tissue without undue destruction of surrounding healthy tissue. For example, prostate cryoablation optimally destroys the lobes of the prostate, while leaving the surrounding neurovascular bundles, bladder neck sphincter and external sphincter undamaged. The prostate is wider at the base and narrow at the apex. A pear or fig shaped ice ball is best for this application. Breast tumors tend to be small and spherical, and spherical iceballs will be optimal to destroy the tumors without destroying surrounding breast tissue. Liver tumors may be larger and of a variety of shapes, including spherical, olive shaped, hot dog shaped or irregularly shaped, and may require more elongated iceballs, larger iceballs, and iceballs of various shapes.
During open chest surgery transmural cryo-lesions can be created on or in the heart to treat cardiac arrhythmia (including atrial fibrillation). A suitable cryoprobe would be useful for this application. Due to the nature of the procedure and anatomical locations that lesions must be placed, the cryoprobe must be sufficiently malleable by the surgeon to be placed on the heart surface but stiff enough such that pressure can be applied without flexing the shaft.
The prior art includes references to malleable and flexible cryoprobes. For example, U.S. Pat. No. 6,161,543, issued to Cox et al discloses the use of a malleable probe. The probe has a malleable shaft. A malleable metal rod is coextruded with a polymer to form the shaft. The rod permits the user to shape the shaft as necessary so that a tip can reach the tissue to be ablated.
U.S. Pat. No. 5,108,390, issued to Potocky et al discloses a highly flexible cryoprobe that can be passed through a blood vessel and into the heart without external guidance other than the blood vessel itself.
Several patents disclose the use of bellows-type assemblies for use with cryosurgical systems. For example, U.S. Pat. No. 6,241,722, issued to Dobak et al, discloses a cryogenic catheter with a bellows and which utilizes a longitudinally movable Joule-Thomson nozzle of expansion. The Dobak ""722 device preferably uses closed media-flow pathways for efficient recycling of the media employed.
Dobak, in his U.S. Pat. No. 5,957,963, disclose the used of a flexible catheter inserted through the vascular system of a patient to place the distal tip of the catheter in an artery feeding a selected organ of the patient. The ""963 patent discloses a heat transfer bellows for cooling the blood flowing through the artery.
U.S. Pat. No. 6,235,019, issued to J. W. Lehmann et al, discloses a cryosurgical catheter having a bellows. The cryogenic catheter has an elongate outer member and a plurality of inner members disposed with the elongate outer member. The inner members define at least one cryogenic path through the outer member. At least one of the inner members has at least one controllable opening formed thereon to selectively release cryogenic fluid. The inner members also include an overtube and an injection tube slideably disposed to one another.
U.S. Pat. No. 6,106,518, issued to Wittenberger et al, discloses a medical device that includes a flexible member having a variable geometry tip with a thermally-transmissive region. A smooth fluid path is provided through the flexible member to and from a variable geometry, thermally-transmissive region. The thermally-transmissive region may be a bellows-like structure.
U.S. Pat. No. 6,224,624, issued to Lasheras et al, discloses a bellows structure used for a selective organ heat transfer device having a flexible coaxial catheter capable of insertion into a selected feeding artery in the vascular system of a patient.
In a broad aspect, the present invention is a malleable cryosurgical probe comprising a cryoassembly for providing a flow of cryogenic fluid and a malleable shaft secured to and in heat transfer relationship with the cryoassembly. The shaft has a bellows portion located thereon formed of a thermally conductive metal. The bellows portion has a plurality of convolutions, the convolutions having outer diameters in a range of 0.140-0.180 inches, and inner diameters in a range of 0.065-0.100 inches. The bellows portion has a minimum bend radius of about 0.195 inches, thus being bendable as desired by the operator.
In another broad aspect, the cryosurgical probe includes a cryostat assembly and a cryoprobe assembly. The cryostat assembly includes an elongated shaft assembly having a bellows portion thereof and a closed distal end. The shaft assembly includes at least one freezing portion comprising said bellows portion, at least one thermally insulated portion and a thermally insulating element positioned about the thermally insulated portion. A cryostat is operably associated with the elongated shaft assembly. It includes a cryostat inlet for receiving gas entering the cryostat, a cryostat outlet and a heat exchanger positioned between the cryostat outlet and the cryostat inlet. The heat exchanger receives gas from the cryostat inlet and provides heat transfer between gas flowing within the cryostat and fluid exterior thereto. At least one Joule-Thomson nozzle is in fluid communication with the cryostat outlet. The at least one Joule-Thomson nozzle expands gas expelled therefrom. The expanded cold fluid communicates with the freezing portion to provide cooling thereof. The cryoprobe assembly includes a handle assembly for supporting the cryostat assembly and a fluid supply line assembly connectable to a fluid source at one end and to the cryostat inlet at a second end. The heat exchanger is positioned at a location longitudinally spaced from the freezing portion(s).
Positioning of the heat exchanger in a position longitudinally spaced from the freezing portion(s) provides the capability of providing malleable segments. The heat exchanger can be made relatively large and powerful providing enhanced operation while concomitantly providing for a freezing portion and/or thermally insulated portion of the elongated shaft assembly that has a small diameter. The bellows portion formed of material that permits reshaping and bending of the elongated shaft assembly as a unit to reposition the ablating surface for greater ablation precision. Moreover, enhancements are disclosed for assuring that there can be bending and reshaping without kinking or collapsing. Such properties are especially imperative for such devices employed in the formation of transmural lesions in anatomical locations that are particularly difficult to access. The malleable segment is sufficiently malleable to be fashioned to the desired shape while rigid enough to retain the shape during clinical use.
Other objects, advantages, and novel features will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.